day1 done

day1/Main.hs

@@ -0,0 +1,50 @@
+{-# LANGUAGE LambdaCase #-}
+module Main where
+
+import Data.List as L
+import Data.Maybe
+import Safe
+
+data InputOptions = Elf1
+                  | Elf3
+                  | Quit
+
+
+getInput :: IO InputOptions
+getInput = do
+  putStrLn "Only get top Elf or sum of top 3 Elf? (1/3/q)"
+  getLine >>= \case
+       "1" -> return Elf1
+       "3" -> return Elf3
+       "q" -> return Quit
+       _   -> putStrLn "not understood" >> getInput
+main :: IO ()
+main = getInput >>= \case
+    Quit -> putStrLn "bye!"
+    Elf1 -> interact $
+          (<>"\n")
+        . show
+        . maximum
+        . fmap (sum . mapMaybe (readMay :: String -> Maybe Integer))
+        . splitOn ""
+        . lines
+    Elf3 -> interact $
+          (<>"\n")
+        . show
+        . sum
+        . take 3
+        . sortOn negate
+        . fmap (sum . mapMaybe (readMay :: String -> Maybe Integer))
+        . splitOn ""
+        . lines
+
+
+-- | Split a list into sublists delimited by the given element.
+--
+-- From: https://hackage.haskell.org/package/haskell-gi-0.26.2/docs/src/Data.GI.CodeGen.Util.html#splitOn
+splitOn :: Eq a => a -> [a] -> [[a]]
+splitOn x xs = go xs []
+    where go [] acc = [reverse acc]
+          go (y : ys) acc = if x == y
+                            then reverse acc : go ys []
+                            else go ys (y : acc)